1. Field of the Invention
The present invention relates to an ultrasonic surgical instrument which has a disposable piezoelectric driver that is detachably connected to an ultrasonic horn.
2. Description of Related Art
Ultrasonic surgical devices are used to perform a variety of different surgical procedures. For example, ultrasonic instruments are used to break and remove a cataracteous lens from a cornea. The ultrasonic instrument typically includes a number of piezoelectric transducers that are mounted to an ultrasonic horn in a single horn assembly. The horn is attached to an outer handle that can be held by a surgeon. A tip or blade is typically attached to the proximal end of the horn. The piezoelectric elements are connected to a number of wires that provide electrical power to the instrument. The piezoelectric transducers convert the electrical energy into a mechanical vibratory movement of the horn and the tip. The vibratory movement of the horn induces a cutting action of the tip.
Ultrasonic instruments must be sterilized after each surgical procedure. Sterilization is typically accomplished by placing the handle, horn and piezoelectric transducers in an autoclave and subjecting the instrument to steam at high pressures and temperatures. It has been found that the high pressures and temperatures within the autoclave will degrade the performance characteristics of the piezoelectric transducers. For example it has been found that after no fewer than one autoclave cycle the electrical to mechanical energy conversion efficiency of the piezoelectric transducers will drop 50%. Because the ultrasonic horn and piezoelectric transducers are provided as one assembled component, both the horn and the transducers must be replaced by a new horn assembly, even though the horn is still functional.
The ultrasonic horns are typically precision devices that are constructed from a relatively expensive material such as titanium. The disposal of the transducers and horn results in an undesirable waste of the horn, which adds to the cost of performing a surgical procedure. Additionally, the output of the instrument during a surgical procedure is unpredictable because of the unknown degradation of the transducers. Some instruments incorporate elaborate monitor and feedback devices that sense the output of the piezoelectric transducers. These devices add to the cost and complexity of the instrument. It would be desirable to provide an ultrasonic surgical instrument that was immune to any degradation of performance because of exposure to autoclave sterilization.